Prevention of corrosion in wells



Aug. 5, 1958 R. c. BUCHAN 6,

PREVENTION OF CORROSION IN WELLS Filed Oct. 11. 1954 Rudolph 6. Baa/ran,

BY A;

IN V EN TOR.

United States Paten PREVENTION-F'CGRROSION'IN'WELLS :Rudolph .C..-..Buchan; Houston, Terr -1 assignor, by memo assignments, .to. Esso:.Researchand Engineering Com= .panyIElizabe'th, N.. J a. corporation. ofDelaware Application October 11,- 1954; Serial-N0-. 4'61",566

-5. Claims. (Cl.:204--148) The present :invention is. directed to amethod for preeventing: corrosioninuwells. More particularly/the=invention is concerned with protecting asteel well casing fromcorrosion-by corrosivewellifluids. In its more specific--aspects,: theinvention isdirected to a'me'thod forprotectinga-steel well casingfromcorrosion by corrosive well-*fluids forming-a *stagnantbodyinthe casing.

The present invention may-be=briefly described-as a method forprotecting a steel well casing from corrosion bycorrosive=well*'fluids-in contact therewith in which a tubing isarranged :having its :loweropen end at a level -a.subst-antial distanceabove a zone.trom..which said corrosive well'fluids are produced. IA,st-agnantbody of said corrosive well'fluids is in contact withjthe steel-casing. The-methodparticularly"comprises lowering a 'retrievable,saerificial metal tubular member; smaller in diameter-than the-tubing,through-the tubinguntil' the tubular 'member projects--a-substantial=dist-ance from the .lower .open-end of thetubing and-extends fromthe-open end of the tubing to.thezonetromvwhich the corrosive wellfluids are produced. The sacrificial metal tubular --mem'ber-.is=anodic- -to-' steel arid is *electrically connected to the tubing. Thetubular member is maintained in the tubing and casing while thecorrosive fluids are produced such that the casing is protected fromcorrosion by the corrosive fluids and the tubular member is corrodedinstead.

The sacrificial metal making up the tubular member may be zinc,magnesium, aluminum and/or alloys of,

these materials, and the like.

The invention contemplates the removal of the tubular memberperiodically from the tubing, while the tubing remains in place, fordetermination of the extent of corrosion taking place in the well. Thecorrosive nature of the well fluids willbe indicated by corrosion of thesacrificial metal and is further contemplated that as the sacrificialmetal tubular member is corroded it may be i replaced by another tubularmember of a metal anodic to steel.

The present invention will be further illustrated by reference to thedrawing in which the single figure discloses apparatus illustrating apreferred mode.

Referring now to the drawing, numeral 11 designates a well bore drilledin the earth to penetrate a plurality of hydrocarbon productiveintervals 12, 13, and 14 which may be separated from each other bynon-productive intervals of zones 15 and 16.

In this particular instance, the well bore 11 has a steel casing 17arranged therein which is cemented in place with primary cement 18. Thecasing 17 has a tubing 19 arranged therein with its lower open end 20above the hydrocarbon productive interval 12. There is provided, forclosing the annulus A between the casing 17 and the tubing 19 a packer21 which may be a packer such as illustrated in the 20th edition of theComposite Catalog on pages 875 and 876 or on pages 496 and 497 of thecatalog, supra, which illustrated Fatented Aug. 5, 1958 'typeillustrated on'pages"875"and-"876 of the catalog,

supra, is schematically shown, such packer comprising upper and 'lower;expandable cup members 1.and Zfixed to retaining rings"3" andfl4,respectively. "The retaining ring 3 is slidable'with respectt0the.tubing.17 and is inwardly; downwardly tapered against the lowerend there- ,of for bearing "engagement with slipsfS to" force such slips"5 into'engagement with the casing"17, as-i'shown.

A "stagnant zone .Z'of' corrosive well fluidsthus-exists below thepacker 21"which maywapiidly .c'orrode;the casing.

In the practice of .the present' invention, an. elongated tubular member22' "is. lowered through the" tubing 19,

such ason awire' line,not"shown,iand secured and/or supported ina'lan'dirignipple, such as 22a, whichj'may be a 'landingnipple,"such.as.described in'thel Composite 20-' "member 22"which"isconstructedof sacrificial imetal'of the :naturedescribed supra is'electrically connected to the tubing 19 by-me-ans" 23 s which "maycomprise 'the' land- Catalogue,"'supra,:at*page'4000. "The tubularextension ing nipple -22w but which will include auuit'a'blemetal tometal band.

The tubularrextension member 22 extends with' its fluids which mayinclude hydrocarbons--..-and:salt-@water.

.aThe,. salt--water: maynbe corrosive due to .the presence of corrosivesalts, sulfides, such as..hydrogen.sulfide,z-.metal sulfides, and the.ilikfifl and-due..to.the.presence,of organic acids, and carbon dioxide:and .the .like. ..The.corrosive .fluids including hydrocarbonsordinarily will proceed upwardly through the tubular member 22 andupwardly through the tubing 19 following'the path described by thearrows and to a zone Z where a relatively stagnant body of corrosivewell fluids will exist which will corrode the casing 17.

In accordance with the present invention, with a sacrificial metaltubular member 22 of the nature described supra anodic to the steelcasing 17 extending from the tubing 19, the steel casing 17 is notcorroded by corrosive fluid in the zone Z above the lower end of thetubular member 22 and the sacrificial metal tubular member 22 iscorroded, thereby protecting the casing 17 from corrosion.

From time to time the tubular member 22 may be retrived from the tubing19 while the tubing 19 is maintained in place and the tubular member 22withdrawn to the well head by engaging the fishing neck 25 with afishing tool carried on a wire line, not shown, and the extent ofcorrosion of the tubular member 22 determined by inspection.Theinspection will also reveal the corrosiveness of the corrosive fluidin the zone Z. If it is determined that corrosion is being suffered bythe corrodible tubular member 22 to the extent that its utility isdestroyed, the tubular member 22 may be replaced by another sacrificialmetal tubular member constructed of a metal anodic to a steel casing 17.

It may be seen from the foregoing description taken with the drawingthat the present invention is of great min, as desired. However, itwould be preferred to construct the tubular member 22 of the sacrificialmetal due to its lightness and due to ease in manipulation andprotection of the casing 17.

The nature and objects of the present invention having been completelydescribed and illustrated, what i wish to claim as new and useful and tosecure by Letters Patent is:

1. A method for protecting a portion of a steel well casing adjacent ahydrocarbon producing formation from corrosion by a stagnant body ofcorrosive fluids accumulated in said portion of said casing byproduction from said formation into said casing, said casing having atubing arranged therein with the lower end of said tubing above saidstagnant body of corrosive fluids in said portion of said casing, whichmethod comprises the steps of metallically, annularly interconnectingsaid tubing with said casing adjacent said lower end of said tubing tothereby establish an electrical interconnection between said casing andsaid tubing adjacent said lower end of said tubing, lowering aretrievable sacrificial metal tubular member smaller in diameter thansaid tubing through said tubing until said tubular member projects asubstantial distance from the lower end of said tubing and extends tosaid portion of said casing containing said corrosive well fluids, saidsacrificial metal being anodic to steel, whereby a galvanic action isestablished in said portion of said casing adjacent said producingformation, and maintaining said tubular member in said tubing and easingwhile said corrosive fluids are produced, whereby said portion of saidcasing is protected from corrosion by said corrosive fluids and saidsacrificial member is corroded.

2. A method in accordance with claim 1 wherein the sacrificial metal iszinc.

3. A method in accordance with claim 1 wherein the sacrificial metal ismagnesium.

4. A method in accordance with claim 1 wherein the sacrificial metal isaluminum.

5. A method for protecting a portion of a steel well casing adjacent ahydrocarbon producing formation from corrosion by a stagnant body ofcorrosive fluids accumulated in said portion of said casing byproduction from said formation into said casing, said casing having atubing arranged therein with the lower end of said tubing above saidstagnant body of corrosive fluids in said portion of said casing, whichmethod comprises the steps of closing the annulus between said tubingand said casing adjacent the lower end of said tubing and metallically,annularly interconnecting said tubing with said casing adjacent saidlower end of said tubing to thereby establish an electricalinterconnection between said casing and said tubing adjacent said lowerend of said tubing, lowering a retrievable sacrificial zinc tubularmember smaller in diameter than said tubing through said tubing untilsaid tubular member projects a substantial distance from the lower endof said tubing and extends to said portion of said casing containingsaid stagnant body of said corrosive well fluids, whereby a galvanicaction is established in said body of said casing adjacent saidproducing formation, and maintaining said tubular member in said tubingand casing while said corrosive fluids are produced, whereby saidportion of said casing is protected from corrosion by said corrosivefluids and said sacrificial member is corroded.

References Cited in the file of this patent UNITED STATES PATENTS1,608,709 Mills Nov. 30, 1926 1,804,078 Baden May 5, 1931 2,149,617Menaul Mar. 7, 1939 2,155,370 Hall et al. Apr. 18, 1939 2,244,322 Zolleret a1 June 3, 1944 2,401,546 Brown June 4, 1946 2,665,759 Childers Jan;12, 1954 FOREIGN PATENTS 523,618 Great Britain July 19, 1940

1. A METHOD FOR PROTECTING A PORTION OF A STEEL WELL CASING ADJACENT AHYDROCARBON PRODUCING FORMATION FROM CORROSION BY A STAGNANT BODY OFCORROSIVE FLUIDS ACCUMULATED IN SAID PORTION OF SAID CASING BYPRODUCTION FROM SAID FORMATION INTO SAID CASING, SAID CASING HAVING ATUBING ARRANGED THEREIN WITH THE LOWER END OF SAID TUBING ABOVE SAIDSTAGNANT BODY OF CORROSIVE FLUIDS IN SAID PORTION OF SAID CASING, WHICHMETHOD COMPRISES THE STEPS OF METALLICALLY, ANNULARLY INTERCONNECTINGSAID TUBING WITH SAID CASING ADJACENT SAID LOWER END OF SAID TUBING TOTHEREBY ESTABLISH AN ELECTRICAL INTERCONNECTION BETWEEN SAID CASING ANDSAID TUBING ADJACENT SAID LOWER END OF SAID TUBING, LOWERING ARETRIEVABLE SACRIFICIAL METAL TUBULAR MEMBER SMALLER IN DIAMETER THANSAID TUBING THROUGH SAID TUBING UNTIL SAID TUBULAR MEMBER PROJECTS ASUBSTANTIAL DISTANCE FROM THE LOWER END OF SAID TUBING AND EXTENDS TOSAID PORTION OF SAID CASING CONTAINING SAID CORROSIVE WELL FLUIDS, SAIDSACRIFICIAL METAL BEING ANODIC TO STEEL, WHEREBY A GALVANIC ACTION ISESTABLISHED IN SAID PORTION OF SAID CASING ADJACENT SAID PRODUCINGFORMATION, AND MAINTAINING SAID TUBULAR MEMBER IN SAID TUBING AND CASINGWHILE SAID CORROSIVE FLUIDS ARE PRODUCED, WHEREBY SAID PORTION OF SAIDCASING IS PROTECTED FROM CORROSION BY SAID CORROSIVE FLUIDS AND SAIDSACRIFICIAL MEMBER IS CORRODED.